Overbased detergents are well described to provide lubricating properties. Often such detergent additives are proportioned with other lubricating additives to provide lubricating oil compositions that exhibit certain desired lubricating properties. Overbased alkali or alkaline-earth metal sulfonates are examples.
European Patent Application Publication No. 1059301A1 describes alkaline-earth aralkylsulfonates having improved detergent and dispersant properties.
International Application WO 97/46644 describes a calcium overbased detergent comprising a surfactant system derived from at least two surfactants, in which at least one of the surfactants is a sulfurized or non-sulfurized phenol, or at least one other of the surfactants is other than a phenol, for example a sulfonic acid derivative, the proportion of phenol in the surfactant system being at least 35% by mass, and the TBN/% surfactant ratio of said detergent being at least 15.
International Application WO 97/46645 describes a calcium overbased detergent comprising a surfactant system derived from at least two surfactants in which at least one of the surfactants is a sulfurized or non-sulfurized phenol, or at least one other of the surfactants is a sulfurized or non-sulfurized salicylic acid, the total proportion of said phenol and of said salicylic acid in the surfactant system being at least 55% by mass, and the TBN/% surfactant ratio of said detergent being at least 11.
International Application WO 97/46647 describes a calcium overbased detergent comprising a surfactant system derived from at least two surfactants in which at least one of the surfactants is a sulfurized or non-sulfurized phenol, or at least one other of the surfactants is other than a phenol, for example an alkylarylsulfonate, the proportion of phenol in the surfactant system being at least 15% by mass, and the TBN/% surfactant ratio of said detergent being at least 21.
International Application WO 99/28422 describes a lubricating oil composition comprising a mixture of at least two detergents containing metals, namely, a) a phenate, sulfonate, salicylate, naphthenate or metal carboxylate, and b) an overbased calcic detergent comprising a surfactant system derived from at least two surfactants in which at least one of the surfactants is a sulfurized or non-sulfurized phenol, or at least one other surfactant is other than a phenol, the proportion of phenol in the surfactant system being at least 45% by mass, and the TBN/% surfactant ratio of said detergent being at least 14.
Alkaline-earth metal hydroxybenzoates are also known as additives for engine lubricating oils.
U.S. Pat. No. 5,895,777 describes lubricating oil additives comprising the alkaline-earth metal salts of aromatic carboxylic hydroxy acids containing carboxylic acids having 16 to 36 carbon atoms.
European Patent Application No. 1,154,012 describes lubricating compositions comprising an oil, an anti-wear additive and a sole oil-soluble overbased detergent comprising an aromatic carboxylate, such as a calcium salicylate substituted by a hydrocarbon remainder.
British Patent No. 1,146,925 describes lubricating compositions comprising, as lubricating agents, polyvalent metal salts, in particular calcium, and alkylsalicylic acids comprising more than 12, preferably 14 to 18 carbon atoms in the alkyl group. These salts can be prepared from the corresponding sodium salts, as synthesis intermediates.
British Patent No. 786,167 describes polyvalent metal salts of oil-soluble organic acids, such as sulfonic hydrocarbons, naphthenic acids or alkylhydroxybenzoic acids, in particular alkylsalicylic acids having an alkyl radical of up to 22 carbon atoms. The alkylsalicylic acids can be prepared from sodium alkylsalicylic acids according to the processes described in British Patents Nos. 734,598; 734,622 and 738,359. The sodium alkylsalicylates described in these British patents are useful as synthetic intermediates for the preparation of alkaline-earth alkylsalicylates, which are also useful as additives for lubricating oil.
In general, the above references describe preparation processes for aromatic carboxylic hydroxy acids and their salts which are derived from alkaline salts of phenol derivatives, such as phenol itself, cresols, mono- and dialkylphenols, the alkyl group having from about 8 to 18 carbon atoms, halogenated phenols, aminophenols, nitrophenols, 1-naphthol, 2-naphthol, halogenated naphthols, and the like.